Challenge of Media Noise Suppression with Oxygen Control in Granular Structure for CoPtCr-based Sputtered Tape towards 400 Gb/in²

A sputtered tape that uses a CoPtCr-based granular recording layer was developed for practical application in the next-generation of large capacity magnetic tapes. The role of oxides in CoPtCr-oxide composite targets in forming nanostructure consisting of magnetic grains and grain boundary oxides for the recording layer was investigated under the distinctive conditions of the roll-to-roll sputtering system. It was confirmed that 1) increasing the amount of Co 3 O 4 in the CoPtCr-SiO 2 -Co 3 O 4 composite target improved the magnetic anisotropy of the recording layer and the magnetic isolation between magnetic grains, 2) the addition of 1.2% Co 3 O 4 content to the target improved the broadband signal-to-noise ratio (BB-SNR) for the tape by 3.0 dB compared with that sputtered by a target without Co 3 O 4 at a linear density of 353 kfci, which was brought by a suppression of noise, and 3) a further added cap layer to this sample brought the higher BB-SNR of 2.3 dB than that for the sample fabricated with the CoPtCr-SiO 2 composite target reported by us in TMRC2017. This SNR improvement was estimated to have the potential to achieve an areal density of 375 Gb/in ² in the case of the application to the latest track-following technology.